This invention relates to buss bar systems. More particularly, this invention relates to surface mounted buss bars, i.e., buss bars mounted on the surface of printed circuit boards.
Several prior art systems exist for supplying power and/or signals to circuit board components. However, these prior art systems all have various disadvantages or drawbacks.
One prior art system uses buss bars mounted in plated through holes in the circuit board. This system has the disadvantage of requiring plated through holes in the board, which are both expensive and have alignment problems.
Another prior art system uses conductive traces on the circuit board to supply power and/or signals to components. This system is characterized by high inductance and high losses (because of long and unopposed surface traces); uses up a lot of the surface area of the board, and prevents interconnection between components on opposite sides of a conductive trace (unless conductive masking is used to bridge the trace). To illustrate the large amount of surface area taken up by a system of this type, a pair of traces (power and ground) and the spacing between them will require a span of from 90 to 250 mills and will run along most of the length or width of the board. This greatly reduces the amount of surface area (sometimes referred to in the art as "real estate" available for component mounting on the board, especially if two or more pairs of traces are used.
Still another prior art system is the four layer board system. In this system, two boards are employed, with each board having circuit components and traces on one side. On one board, the other side is a power layer, while the other side of the other board is a ground layer. The boards are mechanically joined by a nonconductive adhesive bonding the ground and power layers together (which electrically isolates them). While these four layer board systems have low inductance and low loss (because of the opposite directions of current flow in the power and ground layers) they have other drawbacks. They require the use of a large amounts of material, and, hence, are expensive. Also, they require the use of through holes to connect components to power and ground; and hence they have alignment problems. They are relatively complex systems, and the complexities lead to reliability problems.
Several of the prior art systems require external capacitors for noise supression.